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《dna表面密度的計算》由會員上傳分享，免費在線閱讀，更多相關(guān)內(nèi)容在行業(yè)資料-天天文庫。
1、DNA表面密度的計算[1]ThesurfacedensityofDNA,morespecificallythenumberofnucleotidephosphateresidues,iscalculatedfromtheamountofcationicredoxmarkermeasuredattheelectrodesurface.Thesaturatedamountofcharge-compensatingredoxmarkerintheDNAmonolayer,determinedusingchronocoulometry,isdirectlyproportionaltothe
2、numberofphosphateresiduesandtherebythesurfacedensityofDNA.Thismethodpermitsquantitativedeterminationofbothsingle-anddouble-strandedDNAatelectrodes.Surfacedensitiesofsingle-strandedDNAwerepreciselyvariedintherangeof(1-10)*1012molecules/cm2,asdeterminedbytheelectrochemicalmethod,usingmixedmonola
3、yers.Wemeasuredthehybridizationefficiencyofimmobilizedsingle-strandedDNAtocomplementarystrandsasafunctionoftheimmobilizedDNAsurfacedensityandfoundthatitexhibitsamaximumwithincreasingsurfacedensity.WehavequantifiedthesurfacedensityofDNAbytakingadvantageoftheelectrostaticattractionofspecificredo
4、xcationswiththenucleotidephosphatebackbone.TherearetwotypesofinteractionsforsmallredoxmoleculeswithDNA:electrostaticattractionandintercalation.Redoxcationsexchangefornativecounterionsassociatedwiththenucleotidephosphateresiduesoftheprobe.Theamountofredoxmarker“electrostaticallytrapped”attheDNA
5、-modifiedelectrodeisthendeterminedusingchronocoulometry.Atsaturationcoverageoftheredoxmarker,thesurfacedensityoftheprobeiscalculatedassumingcompletechargecompensationoftheDNAphosphateresiduesbyredoxcations.Astrongappealofthisapproachisthatthismeasurement,unlikemeasurementsusingothernoncovalent
6、labels,isinsensitivetoboththebasecompositionandthechainorder(single-strandedvsduplex).Themeasuredredoxmarkerisdirectlyproportionaltothenumberofphosphategroupspresentatthesurface.Anattractiveaspectofchronocoulometry(計時庫倫分析法)isthatthedoublelayerchargeandthechargeduetoreactionofspeciesadsorbedont
7、heelectrodesurfacecanbedifferentiatedfromthechargeduetoreactionofredoxmoleculesthatdiffusetotheelectrodesurface.MCH的作用：liftstheDNAfromthesurfacetoaconformationwhereeachprobeisimmobilizedsolelythroughthethiolate.[1]固定DNA及MCH的方法[2]：atwo-s
